Assuming they are the original bolts, go to your local MB dealer with the V5 and proof of ID. They have a master set of keys and will order the correct one for you.
The wheels have been changed and are not original so I'm pretty certain the nuts aren't either but they still look like Mercedes so maybe still worth a try
hope this helps...i didnt get locking key with my car....original MB nuts went to local dealer ..parts dept..just turned up with car they had master set of 24 tried them bingo ...had spares in stock £15.00...... could be worth a try depends on pattern of the nut
I might try my local MB dealer but not sure if I'll have any luck as the wheels have definitely been changed at some point as they aren't original but still worth a try.
There are 25 , I had to go and get one last year after leaving mine at the side of the road. MB Tech came out , started at number one and just went through thill he found the right one.